Interlocking system for railroads



April 26, 1938. c. F. sToLTZ 2,115,511

I INTEHLOCKING SYSTEM FOR RAILROADS Filed oct. 25, 1929 2 sheets-sheet 1 l on n2 molaH 0mm @E m92 a. E m. wcou H mi -H W e m5 /f/a/ATTORNEY April 26, 1938. c. F. sToLTz' INTEELOCKING SYSTEM FOR RAILROADS Filed Oct. 25, 1929. 2 Sheets-Sheet 2 NE\ oww mnrvu XIII@ V o: Il hwl lNVEg/yR BY @d TTORNEY Patented Apr. 26, 1938 UNlTED STATES PATENT OFFICE INTERLOCKING SYSTEM FOR RAILROADS' Application October 25,

30 Claims.

any number of track sections, is set up for a train to pass through an interlocking plant which route cannot be changed after a train has accepted the governing signal except under certain 20 predetermined conditions. However, it is desirable, in order to prevent delay, that each of the track sections included within the route shall be obtainable for new routes as soon as the train leaves these sections, and this interlocking feature is termed sectional route locking.

With the above and other considerations in mind, the present invention proposes to provide an improved sectional route locking system for use in interlocking plants, More specically, the present invention proposes to provide electric circuits interlocked through relays and the like for interrelating the operation oi the various signals, switches, and the like of an interlocking plant. One group of relays and associated circuits are to establish what may be termed as directional routes, that is, certain of the relays are affected only when a route is set up in one direction and certain other of the relays are affected only when a route is set up in the opposite direction. By the interlocking of the signal control circuits with these directional route relays, a train is given head-on protection, or in other words, two routes opposing each other in direction cannot be set up. Another group of relays and circuits are to establish the approach locking for the track switches, which relays and circuits, when combined with the directional route locking relays, provide that a route cannot be taken away from a train after it has been accepted, except under predetermined conditions, and also provide thata particular section shall be released to be used at the will of the operator immediately after becoming unoccupied.

A further object of the invention is to provide means whereby a particular-route may be manuas route locking, that is, a route, composed of 1929, Serial N0. 402,527

ally released with the train on the route to allow another train or engine to proceed towards the rst train under control of governing signals so that the two trains may be coupled together.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, in which similar reference characters are used to designate similar devices with each having distinctive exponents that are used to distinguish the group of devices to which the particular device belongs, and in which Figs. 1 and 1A when placed end to end comprise one complete diagrammatic representation of a stretch of railroad track, including track switches and associated signals, as electrically interlocked by the devices and circuits constructed and arranged in accordance with the present invention.

With reference to the accompanying drawings, a stretch of track at the entrance and exit of an interlocking plant is shown as including track sections T", T2, T4, T6, and T8, each of which is provided with the usual track battery and track relay (not shown) with the condition of these track sections, as given by the track relays, repeated in the interlocking tower by track repeater relays TRO, TR2, TR4, TRB, and TR8 respectively. It will be noted, that for convenience only the track repeater relay TR8 has been indicated as governed by the conditionsl of its respective track section T8.

The track section T2 contains a track switch TSa which, when reversed, allows the passage of traiiic onto a turn-out track section TOe; and, similarly the track section T6 contains a track switch TS1 which, when reversed, allows the passage of traffic onto a turn-out track section TOb. These track switches TSa and TS are controlled to normal or reverse extreme locked conditions by their respective switch machines SMa and SM1.

The east bound traffic over track section T2 is governed b-y a dwarf signal S3 which is of the two indication type for governing low speed routes, while a signal S7 is a high signal of the three indication type for governing the passage of east bound traffic over the track section T6, as this track section is the exit of the interlocking plant and the entrance to high speed automatic block signal territory. A dwarf signal S9 of the two indication type is provided for governing west bound traflic over the track section T6.

Likewise, a dwarf signal S of the two indication type is provided for governing west bound traic over the track section T2.

In the interlocking tower, a miniature track layout, identical in every respect to the actual track layout in the interlocking plant, is provided with track sections t0, t2, t4, t6, and t8. Also, the turnout track sections TOa and TOb are similarly represented by the turn-out track sections toa and tob. The signals governing traic are represented on the track diagram by the usual signal symbols of which symbols s3, S5, S7, and S9 are shown in locations corresponding to the locations of the respective trackway signals. Preferably this miniature track layout should include indicator lights to indicate the occupancy of a particular track section by a train, but which lights have been omitted for the sake of clearness in setting forth the present invention. Indicator lights can also be provided to give the indications displayed by the signals S3, S5, S7, and S9 respectively but said lights likewise have been omitted to simplify the disclosure.

Signal levers SL3, SL5, SL7, and SL9 are located beneath the symbols which represent the respective signals which they control. These signal levers control contacts which are normally open with the levers SL in normal positions as shown, and which are closed with the levers in righthand dotted line positions and remain closed until they are manually moved from such positions. Switch machine levers SMLa and SMLb are provided for controlling their respective switch machines SM5 and Slvlb by operating their respective contacts to either of two extreme positions which positions are maintained until said levers are manually moved.

A push button PB of the usual self-restoring type is located beneath track section t4 for releasing the route set up for a train standing on that track section. A time element release TE is provided for manually releasing a time element mechanism to open certain contacts and close certain other contacts a pre-determined time thereafter. This time element operated contact mechanism TEC may be a plunger and valve arrangement as shown, a mechanical clock work device or any other well known mechanical means for accomplishing the result.

Lever relays R3, R5, R7, and R9 are provided to repeat the condition oi" the associated signal levers SL. Also, relays SSEL and SSb are the usual switch repeating relays located in the tower to indicate the position and locked condition of their respective track switches TSa and TS". These relays SS5 and SSb are of the three position polarized type having their contacts operated to right or left hand positions in accordance with the normal or reverse positions of their respective track switches. These relays are energized over individual polarized circuits controlled by the usual point detector or switch box contacts for the respective switches so as to apply one polarity or the other to the corresponding relay in accordance with the extreme locked position of the track switch. When a track switch is in an intermediate unlocked position or is in operation, the corresponding SS relay is deenergized and the contacts of that relay assume neutral positions. With each of the signals S3, S5, S7, and S9, are associated home relays HB5, HB5, HR7, and HR9 respectively which, when energized, cause the least restrictive indications of the associated signal to be displayed, such for example as yellow in the case of the dwarf signals. When these HR relays are deenergized, the most restrictive indication of the respective signal is displayed, such for example as red. The indications of the various signals S have been conveniently indicated by showing or repeating the lights at the HR relays rather than carry the wires to the respective signals.- It will be noted, however, that the relay HR9 is shown as directly controlling the signal S9 to illustrate specifically what is intended. Also, the relay HR7, when energized, permits either the green or the yellow indication to be selected in accordance with the energization or deenergization of a distant relay DR7 which is controlled by the home relay of the next succeeding signal location in accordance with the condition of the automatic block signals located outside the interlocking plant i-n the usual manner well known to those skilled in the art.

The approach locking group of relays includes, thermal time element relays THS, TH5, and TH9 associated with their respective signals as their distinctive exponents indicate, and thermal stick relays THS3, THS5, and THS-9, that is, relays which have stick circuits governed by their respective thermal relays. A similar arrangement of a thermal time element relay, used in conjunction with a stick relay to produce a time element approach locking means, is shown and described in an application by S. N. Wight Ser. No. 389,446 iiled August 30, 1929, now U. S. Letters Patent 2,038,504. Thus the various ways, in which such a combination may be used will not be explained except as pertains to the present invention.

The group of directional stick route relays for the east bound route includes, relays ES2, ES4, and ESG, while the west bound group includes relays WS2, WS4, and W56. A track repeater stick relay TRS6 is used in conjunction with the track repeater relay TR5 to maintain a stop indication at signal S7 after a train has passed said signal until it is again manually cleared by the operator. Ihis signal S7 also has an approach locking stick relay AS7 to provide that once the signal S7 has been cleared and a train has accepted the route, said route can not be altered except after the release of the time element contacts TEC. A stick relay PBS4 is associated with the push button PB to maintain the condition established by said push button until certain conditions have been restored to normal.

The switch machines are controlled from their respective levers in the usual manner which has been shown more specically for the switch machine SMb. This control, of course, can be repeated for the switch machine SMa but for convenience is only indicated. The promiscuous or unauthorized control of the switch machines SMn and SMb is prevented by lock relays LRe and LRb respectively which relays are of the slow acting type and are energized by the movement of a proper switch machine lever SML to a new governing position providing the associated track section and route established are in proper conditions, as indicated by the respective directional stick route relays'and the track repeater relay of the track section in which the track switch is located.

It is believed that the usefulness and the various interrelated functions and operations of such a system will be more readily understood by further describing the system from the standpoint of operation.

Operation of the system The system is shown in a normal condition with the track switches TSa and Tb in normal positions permitting the passage' of traffic over the main track in accordance with the governing signals. This information concerning the track switches is repeated or indicated in the interlocking tower by the respective 5S relays with each of said relays having its polar contacts energized to right hand extreme positions. Also, as all the track sections are unoccupied, the track repeater relays TR will indicate this condition in the interlocking tower by assuming energized positions. The various signal control levers SL are in their normal at stop positions, thus deenergizing the relays R which in turn deenergize the f relays HR. With the HR relays deenergized, the

most restrictive indication of each signal will be displayed, which fact may be indicated in the interlocking tower by suitable indicating lamps on the miniature track diagram (not shown). Also, the switch machine levers SML are shown in their normal positions in correspondence with the normal positions assumed by their respective track switches TS. With the track repeater relays TR. and the home relays HR in their normal positions, the thermal stick relays THS will assume energized positions which in turn cause the various directional stick route relays ES and WS to be energized through their respective circuits. These various conditions and circuits are maintained with the system in the normal condition, as above stated, by circuits and devices operating as more specifically pointed out below.

The control wires of the relays have been indicated as supplied with suitable electrical energy from suitable sources which, for convenience, have only been indicated as the positive and negative terminals of suitable sources by reference characters B+ and B+ respectively. It is to be understood that these sources may be either alternating current or direct currentin any suitable way to meet the requirements of practice without in any manner affecting the present invention.

The relay THS3 is energized through a circuit traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through back contact il! of relay HR3, wires and l2, front contact |3 of track repeater relay TRO, wires |4, l5, and I6, winding of relay TH53, to the negative terminal of the suitable source indicated as B+. The contacts of the relay THS3 are thus maintained in energized positions which completes an energizing circuit for the relay E52 that is traced as follows:- from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact B ofV relay TESS, wires and I8, front contact |9 of relay TR2, wires 20 and 2|, winding of relay E52, to the negative terminal of the suitable source indicated as B+. With the contacts of relay E52 in an'energized position, the energizing circuit for the relay E54 is completed, which is traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact 22 of relay'ES2, wires 23, 24, and 25, front contact 23 of track repeater relay TR4, wires 21 and 23, winding of relay E54, to the negative terminal of the suitable source indicated as B+.

The approach locking stick relay A5'7 is energized through a pick-up circuit traced as followsz--from the positive terminal of a suitable source of electrical potential indicated as B+, through back contact 8| of relay HR", Wires 32 and 33, `front contact 34 of `relay E54, wires 35,

36,l 31, and 38, winding of relay AS'I to the negative terminal of the suitable source indicated as B+. The raising of the contacts of relay A5'I completes the energizing holding circuit of the relay ES6 which is traced as followsz--from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact 40 of relay A57, wires 4| and 42, front contact 43 of relay TRB, wires 44 and 45, win-ding of relay E56, to the negative terminal of the suitable source indicated as B+.

The relay THS9 is energized through a circuit traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through back contact 50 of relay HRB, wires 5| and 52, front contact 53 of relay TR2, wires 54, 55, and 56, winding of relay THS9, to the negative terminal of the suitable source indicated as B+. With the contacts of relay THS9 in energized positions, the energizing circuit for relay W56 is traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact 51 of relay THSQ, through wires 58 and 59, front contact 60 of relay TRS, wires 6| and 62, winding of relay W56, to the negative terminal of the suitable source indicated as B+. With the contacts of relay WS6 in energized positions, the energizing circuit for W54 is traced as follows:- from the positive terminal of a suitable source of electrical potential indicated as B+, through front Contact 65 of relay W56, wires 66, 6T, and 68, front contact 69 of relay TR4, wires 'IIJ and 1|, winding of relay W54, `to the negative terminal of the suitable source indicated as B+.

The relay THS5 is energized through a circuit which is traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through back contact 13 of relay HB5, wire 74, front contact of relay W54, wires 16, 11, and 7S, winding of relay THS5, to the negative terminal of a suitable sourceindicated as B+. With the contacts of relay THS5 in an energized position, the energizing circuit for the relay W52 is traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact 80 of relay THS5, wires 8| and 82, front contact 83 of relay TR2, wires 84 and 85, winding of relay W52, to the negative terminal of the suitable source indicated as B+.

The track repeater stick relay TRS6 is energized through a circuit which is traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact 83 of relay TRG, wires 9|) and 9|, back contact 92 of relay R", wires 93 and 94, winding of relay TRSG, to the negative terminal of the suitable source indicated as B+.

The above description points out those pick-up circuits upon which the system is dependent for establishing the normal conditions of the various devices included in the system. The various circuits that are closed during the operating conditions dependent upon the movement of control levers and the passage of trains will be pointed out and described more specifically in considering typical operations of the system.

However, there are various auxiliary circuits which are closed while the system is in its normal condition, which auxiliary circuits have their usefulness more particularly during the operation of the system and will therefore be more readily understood by reference to the description pointing out certain typical operations.

For example, the relays THS3, THSD, and THS9 have auxiliary stick circuits including front contacts 95, 9E, and 99 respectively. These stick circuits include the thermal elements of their corresponding thermal relays THG, THD, and TH9 respectively, but the current which flows in these auxiliary stick circuits is insufficient to actuate the thermal element relays. The function of these stick circuits is more particularly pointed out hereinafter in connection with the clearing of signal S9 for allowing the passage of a train in a west bound direction.

Further, the relay AS7, which functions similar to the relays THS but is associated with a mechanical time element relay TEC, has a stick circuit closed from B+, through back contact 3| of relay HB7, wires 32, |84, |85, and |80, front contact |81 of relay ASV, wires |88 and 38, windings of relay AS'l, to B-. This stick circuit serves a similar purpose as the stick circuits of the thermal time element stick relays THS.

Also, the relays WS2, WS4, WSG, ES2, ES4, and ESG are provided with stick circuits including front contacts |90, |9|, |92, |93, |94, and IGI respectively. These stick circuits for the respective relays serve to shunt the front contact of their corresponding track repeating relay for purposes more specifically explained hereinafter.

The track repeating stick relay TRSG is provided with a stick circuit closed from B+, through front contact 89 of relay TRG, wires 90 and |95, front contact |96 of relay TRSG, wires |91 and 94, windings of relay TRSG, to B-. This stick circuit serves to shunt out the back contact 92 of relay R7 for the purpose of causing the signal S7 to be a stick signal, as hereinafter pointed out.

Let us assume that the operator, in anticipating the entrance of a train in a west bound direction into his interlocking territory, desires to set up a route onto the turn-out track TOD. As the signals, governing traffic over the track section TG including track switch TSD, are at stop, the first act necessary for the operator will be to operate the switch machine lever SMLD to a dotted line reverse position. This will immediately operate the switch machine SMD as the approach locking time element of the thermal relay TI-I9 is ineffective due to the fact that there is no train upon the track section T9 approaching the signal S9 to accept its indication; and also due to the fact that the signal S9 is giving a stop indication. In other words, should a train enter the track section TG to receive an indication from the signal S9, the track repeater relay TR9 would be deenergized opening its front contact 53 which is included in the circuit of the relay THS9 as heretofore traced. However, a multiple path or a stick circuit including the winding of the thermal relay TH9, wire 98, front Contact 99 of relay THS9, and wire |00, provides that the relay THS9 shall remain in an energized position although a train is approaching, so long as the signal S9 continues to give a stop indication.

Let us assume that a train is approaching the interlocking plant in a west bound direction and treads upon the track section TG, which fact is indicated to the operator who then proceeds to set up the route onto the turn-out track TOD as heretofore mentioned. He operates the switch machine lever SMLD to a reverse dotted line position which operates its contacts |02 and |03 to reverse dotted line positions. As the contact |02 passes its central intermediate position, contact is made for a suflicient length of time to completely energize the lock relay LRD through a circuit which is traced as followsI-from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact |05 of relay WSG, wire |06, front contact |01 of relay TRSG, wire |08, front contact |09 of relay ESS, wire |0, central contact |02, wire winding of relay LRD, to the negative terminal of the suitable source indicated as B-. The relay LRD is of the slow releasing type remaining a sufficient period of time in an energized condition to complete the reverse operating circuit for switch machine SMD after the contact |03, controlled by switch machine lever SMLD, reaches its dotted line reverse position. This reverse energizing circuit for the switch machine SMD is traced as follows:-from the negative terminal of a suitable source of electrical potential indicated as B+, through reverse contact |03 of lever SMLD, wire ||3, front contact of relay LRD, wires |5 and H6, through the operating mechanism of the switch machine SM, wire ||1, front contact ||8 of relay LRD to the mid-point, or half voltage tap of the suitable source, known as the common terminal and designated as C. This circuit is completed for a suicient period of time to effect the complete control of the switch machine SMD. The switch machine SMD now controls the track switch TSD to a reverse position. When the lock relay LRD becomes deenergized, the control line Wires ||6 and ||1 for the switch machine SMD are shunted through back contacts ||4 and H8, and through wires ||9 and |20 respectively, which prevents any foreign currents from falsely operating the switch machine.

The train is now approaching the signal S9, and as the track switch TSD is in a reverse locked position, as indicated by relay SSD, the operator may clear the signal S9 by moving the signal lever SL9 to the dotted line position.

With the signal lever SL9 in the dotted line position, the relay R9 is energized through closed contact |2| as is obvious from the drawings. The energizing circuit for relay HR9 is now traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through the various signal control circuits (not shown) associated with the turn-out track TOD similar to those shown for the main track, through contact |22 of relay SSD in a reverse dotted line position, wire |23, front contact |24 of relay R9, wire |25, winding of relay HR9, wire |26, front contact |21 of relay R9, to the negative terminal of the suitable source indicated as B-. The relay HB9 is now energized, which completes the energizing circuit for the yellow indication of signal S9 from the positive terminal of a suitable source of electrical potential indicated as B+, through front contact |28 of relay HB9, wire |29, yellow indicator lamp of signal S9 to the negative terminal of the suitable source indicated as B-.

Also, the stick circuit for the relay THS9 is opened at back contact 50 of relay HR9. The dropping of Contact 51 of relay THS9 opens the energizing circuit of the relay WSG as heretofore traced, thus opening front Contact |05 of relay WSG, which prevents the energization of lock relay LRD in the event that the operator should promiscuously or unintentionally attempt to operate the switch machine lever SMLD to the normal position. 'Ihe opening of front contact 65 of relay WSG opens the energizing circuit of the relay WS4 as heretofore traced, but as the track switch TSD is in a reverse position which condition is indicated by the relay SSb for reasons previously explained, the relay WS4 now has an energizing circuit traced as followsz--from the positive terminal of a suitable source of electrical potential indicated as B+, contact |30 of relay SSb in a reverse position, wires |3I, 61, and 08, front contact 69 of relay 'IR/.4, wires 10 and 1|, winding of relay W54, to the negative terminal of the suitable source indicated as B+.

As the train passes over the track section T6 onto the turn-out track TOb, the track repeater relay TR6 is deenergized which opens the energizing circuit for relay TRSG at the front contact 89 of relay TRB. The deenergization of relay TRS6 opens its front contact |91 which further insures deenergization of the lock relay LRb. Thus, the switch machine SlVlb is efectually prevented from unauthorized operation.

Let us now consider that the train has passed off from the track sections 'I8 and T6, so that the track repeater relays TR8 and TR6 have again been energized. With the track repeater TR,6 energized, front contact 89 again closes the energizing circuit for relay TRSG, as heretofore traced, which, when energized, closes front contact |01. The operator having been given an indication of the passage of the train over track section T6, returns the signal control lever SL9 to a normal position which deenergizes relay HB9, thus closing the energizing circuit for relay THS9 through backcontact 50 of relayfI-IR9 and front contact 53 of track relay TRS. The energization of relay THS9 closes front contact 51 which again energizes relay W86 through the same circuit as heretofore traced which closes its front Contact |05. The energizing circuit of relay LRb may now be completed by movement of the control lever SMLb to a normal position which operates the switch machine SMb and track switch TSb to normal positions. The normal locked position of the switch TSb is indicated by the relay SSb which breaks the energizing circuit of the relay WS4 through the reverse contact |30, but a circuit for relay WS4 is closed through front Contact 65 of relay WSG which is now energized. Thus, it is obvious from the above description, that the normal operation of the interlocking system in setting up a route for a train and safe-guarding its passage over the route by preventing unauthorized changing of that route is accomplished in a safe and eflicient manner. Also, as soon as the train leaves the particular section, that section may bev immediately used for another route without the loss of any time.

If the operator, noting the approach of a train on track section T9, had reversed the track switch T59 and cleared the signal S9, as above explained, and then changed his mind for one reason or another causing the signal S9 to Ygive a stop indication, he could not return the track switch TSb to a normal position except after a predetermined time as governed by the pick-up time period of the thermal relay TH9. This is true because the relay HR9 having been energized would have opened the stick circuit of relay THS9 at the opened back contact 50 of relay HR9 deenergizing the relay THS9 and thus opening its stick energizing circuit at front contact 99 of relay TI-IS9. The circuit forenergizing the relay LRb is opened as heretofore explained. The train, being upon track section T9, causes the front Contact 53 of relay TR3 to be in a retracted position. rIhus, when the signal S9 is returned to the stop indication in the face of the oncoming train, energy is placed upon the winding of the thermal relay 'Tl-I9 through a circuit traced as follows:-from the positive terminal ofy a suitable source of electrical potential indicated as B+, through back contact 50 of relay HB9, wire 5|, thermal winding of relay TH9, wire 99, back contact 99 of relay THS9, to the negativeV terminal of the suitable source indicated as B-. As the winding of the relay TH9 is now across: the terminals of a suitable source of potential, the current flow is suflicient to heat its thermal elements causing its contacts |82 and |83 to close after a predetermined period of time which closes a pick-up circuit for the relay THS9. This pick-up circuit includes contacts |82 and. |83 which bridge the open contacts 53 and 99 as is obvious from the drawings. The energization of relay THS9 effects the partial completion of the energizing circuit for relay I Rb which may be completed by the movement of lever SlVl'LD operating contact |02. However, this cannot be accomplished except after the predetermined time mentioned which is sufficient for the train on track section T9, if at the entrance to the section, to come to a stop in the face of signal S9; or, should the train pass the signal S9, having received its indication too tardily, the time element would be sufficient for the train to deenergize the track repeater relay TR6 which then deenergizes relay TRS6 and thus opens the energizing circuit of lock relay LRD at front contact |01 of relay TRS6 in time to prevent the control of the switch TSb beneath the moving train.

Let us againconsider that the system is in a normal condition as originally set forth, and that the operator is switching a train through various routes of the interlocking plant which at this time enters the track section T0. In view of this, the operator clears the signal S3 to allowthis train to proceedin an east bound direction. However, shortly thereafter a high speed passenger train for example, enters on the track section T8, that the operator desires to allow to enter the interlocking plant with as little time delay as possible, and thus immediately operates the signal lever SL9 to a dotted line position to clear the signal S9 without thinking of the i'lrst train which has accepted the signal S3. Such an exigency produces no particularly unsafe condition as the signal SL9 is prevented from assuming a clea'r condition, thus stopping the passenger train before any harmful result is accomplished. The manner in which the stated result is accomplished will now be explained.

With the Switch TS9 in a normal position, the lever SL3 will bei in a dotted line position to clear the signal S3; The relay R3 is energized through contact |35 as is obvious from the drawings. The relay HIB'.3 is energized through a circuit traced as followsz-frorn the positive terminal of a suitable source of electrical potential indicated as B+, through front contact |36 of relay W84, wires |31 and |33, back Contact |39 of relay R5, wire |49, contact MI of relay SSa in a right-hand normal position, wire |42, front contact |43 of relay R3, wires |04 and |45, winding of relay HB3, wire |46, front Contact 148 of relay R3, to the negative terminal of the suitable source indicated as B+. The yellow indication of the signal S3 is given `with contact |50 of relay fm1* in an energized position. Also, the energizing circuitfor the relay THS3 is broken at back contact |0 of relay HR3. This in turn opens the energizing circuit of relay ES2 at the front contact 8 of relay THS9, which condition in turn `opens the energizing circuit of relay ES4 at the front contact 22 of relay ES3.

As heretofore assumed, the operator moves the lever SL9 to a dotted line position intending to clear the signal S9. The relay R9 is energized but fails to energize the relay I-IR9 to clear the signal S9 because of the deenergization of the relay ES4 in accordance with the route set up for the train proceeding in an east bound direction. It is pointed out that, if the train proceeding in the east bound direction were not present and the east bound route were normal, the relay HR9 would be energized through a circuit traced as follows-from the positive terminal of a suitable source of electrical potential indicated as B+, through iront contact |5| of relay ES4, wires |52 and |53, back contact |54 of relay R9, wires |55 and |56, time element contact |51 in a normal position, Wire |58, contact |22 oi relay SSb in a right-hand normal position, wire |23, front contact |24 of relay R9, wire |25, winding of re lay HB9, wire |26, front contact |21 of relay R9, to the negative terminal of the suitable source indicated as B+. Inasmuch as the relay ES4 is deenergized due to the clearing of signal S3, the energizing circuit for the relay HR9 is opened at front contact |5| of relay ES4. The passenger train proceeding in a west bound direction is thus caused to stop at the signal S9 preventing any unsafe condition.

Again considering that the interlocking system is in the normal condition as shown, let us assume thata train is proceeding in a west bound direction entering the interlocking plant on the track section T9. Further let us assume that this interlocking plant, for example, is the end of the divisional run and the train at this point must change engines. The operator clears the signal S9 and allows the train to proceed over the track section T6 onto the track section T4 at which point the train stops in accordance with the stop indication given by the signal S5. The operator then clears the signal S5 which allows the uncoupled engine to proceed in a westward direction to some other part of the interlocking plant. In due time, an engine backs onto the track section T9, in readiness to be coupled to the train standing on track section T4. Under normal conditions the operator could not clear the signal S3 due to the train which is standing on the track section T4. In other words the train from the east deenergizes the relay WS4, thus opening the energizing circuit for the relay HB3 at front contact |35 of relay WS4. However, the present invention provides special means for such occasions. The signal S3 is capable of being cleared if the push button PB is depressed, as this energizes the relay PES4 which relay is maintained energized through stick circuits as long as either the relay WS4 or ES4 is deenergized. The energization of the relay PES4 places positive potential upon the energizing circuit for the relay HR3.

More specifically, the lever SL9 is placed in a dotted line position closing contact |2| and energizing relay R9 as heretofore described. The relay HR9 is now energized through front contacts |21 and |24 of relay R9, normal contact |22 of relay SSD, normal contact |51 of time element contactor TEC, back contact |54 of relay R, and iront contact |5| of relay ES4. The energization of relay HR9 deenergizes the relay THS9 at back contact 50, which in turn deenergizes the relay WS6 at front contact 51 of relay THS9, which in turn deenergizes the relay WS4 at front contact 65 of relay WSS. The train now passes in a westward direction in accordance with the signal S9 and treads upon the track section T9 and T4 coming to stop in approach to signal S5. It will be noted that, although the track repeater relays TR6 and TR4 are deenergized, the east bound directional relays ES4 and ES6 are not deenergized as they are maintained energized through stick circuits, for example, ESG is energized with the track repeater TR9 deenergized opening the circuit as heretofore traced at front contact 43, which is shunted as is obvious from the drawings, by the stick circuit including wire |66, front contact |6| of relay ES6 and wire |62. The other directional route relays are similarly held in energized positions through their stick circuits when a train passes in a direction opposite to the one under which they are supposed to be deenergized. In other words, their pickup circuit includes a contact of a track repeater relay which may be deenergized without deenergizing the associated directional route relay once said relay has been energized to close its stick circuit. It is of course understood that the directional route relays are deenergized as heretofore mentioned.

As the train cornes to a stop on the track section T4, the operator may clear the signal S5 by moving a lever SL5 to a dotted line position closing contact |65 which energizes the relay R5 as is obvious from the drawings. The relay HR5 is now energized through a circuit traced as followsz-from the positive terminal of a suitable source of electrical potential indicated as B+, through back contact |43 of relay R3, wire |42, Contact |4| of relay SS3 in a right hand normal position, wire |40, front contact |39 of relay R5, wires |66 and |61, winding of relay HB5, wire |68, front contact |69 of relay R5, to the nega-v tive terminal of the suitable source indicated as B-. The signal S5 is now caused to display a yellow indication with its Contact |16 in an energized position which is obvious from the drawings.

After the engine is uncoupled from the train, it may proceed in a west bound direction in accordance with the signal S5 and with any other signals which it may encounter on its way through the interlocking plant.

We will now assume that the reserve engine is proceeding in' an east bound direction to be coupled to the standing train and approaches the signal S3 which cannot at this time be cleared although the signal S5 is returned to a stop position by moving the lever SL5 to its present normal position, as the energizing circuit for the relay HB3 is opened at front contact |36 of relay WS4.

The operator now depresses the self-restoring push button PE which energizes the relay PES4 through a circuit which is traced as follows:- from the positive terminal of a suitable source of electrical potential indicated as B+, through back contact |36 of relay WS4. wires |1| and |12, winding of relay PES4, wires |13 and |14, push button PB in a depressed position, to the negative terminal of the suitable source indicated as B+. The relay PES4 is held in an energzed position, although the push button PE is automatically restored toI a non-contacting position, through a stick circuit traced as followst-from the positive terminal of a suitable source of electrical potential indicated as E+, through back contact |35 of relay WS4, wires |1| and |12, winding of relay PES4, wires |13 and |15, iront contact |16 of `relay PES4, to the negative teri minal of the suitable source indicated as B.

The relay HB3 may now be energized through a circuit traced as follows:from the positive terminal of a suitable source of electrical potential indicated as B-|-, through front contact IBii of relay PBS4, wires |81 and |38, back contact |39 of relay R5, wire |40, contact |4| of relay SSa in a right-hand normal position, wire |42, front contact |43 of relay R3, wires |44 and |45, winding of relay HB3, wire |46, front contact |48 of relay R3, to the negative terminal of the suitable source indicated as B-. The signal S3 now gives a clear proceed indication with the contact |50 of relay HR3 in a raised position. With the relay HB3 energized, the relay THS3 is deenergized at back contact IU of relay HRS, which in turn deenergizes the relay ES2 at front contact 8 of relay THSL', which in turn deenergizes the relay ES4 at front contact 22 of relay ES2. The reserve engine accepts the signal S3 and is coupled with the train standing on track section T4. The operator may now return the lever SL3 to a normal non-clear position causing the signal S3 to give a stop indication. Also, the signal lever SL5 is moved to a clear position energizing relay R5 which in turn causes the relay HRSto be energized through its circuit, as heretofore traced, including front contacts l|39 Aand |69 of the relay R5, contact |4| of relay SSa in a right-hand normal position and back contact |43 of'relay R3. When the train has proceeded over the track section T2, onto the track section To and thence onto the various other track sections included in its route in a West bound direction out of the interlocking plant, the signals S3, S5, S7, and S9 may be returned to their normal stop conditions which restores the relays of the interlocking plant -to their normal positions opening the stick circuit of relay PBS4 at back contact |323 of WS4 and back contact |5| of relay RS4 so that the system assumes a full normal condition.

When a train proceeds in an east bound direction through the interlocking plant, the signal Srl is caused to give a clear indication, it is assumed, in accordance with the conditions of traic ahead inthe automatic block signal territory outside the interlocking plant, as indic-ated in the interlocking plant 'by a directional relay DR". This relay DR'7 is controlled through the contacts of the home relay at the next signal located outside the interlocking plant. The track relay TRS6 causes this signal S7 to be a stick signal, that is, to continue to give a stop indication after the train has passed beyond its track section T6 until the operator again causes it to give a clear indication. Also, the time element contactor TEC is employed to give an approach locking time period similar to that furnished by the thermal relays TH but of longer duration to take care of the higher speed trains which the high speed three indication signal governs. However, as it is no part of the present invention to employ stick signals, which are well known to those skilled in the art, or manual release time contactors as are often used, the operation and description of such a combination will not be described in detail. Such a combination is merely shown in connection with the present invention to show the adaptability of the present invention to the various conditions met in an interlocking plant of the usual type.

It is to be understood from the foregoing 'that semi-automatic signals could be used at the "several locations shown without in any manner af- `fecting the present invention. Also, the present disclosure shows only the circuits and devices associated with a stretch of main track; and it is to be understood that similar circuits may be associated with the turn-out track sections without in any manner affecting the operation of the system or departing from the present invention. It may be further stated that the control of the signals may be of the remote type or the direct control type whichever most advantageously ts the circumstances to be met.

It is obvious from the above description that an interlocking system has been provided with approach locking and with sectional release route locking which is accomplished by establishing directional routes by the combination oi relays and devices which are used, with only those devices which are governed by the particular direction of the route set up being affected at one time. Also, the interlocking system, as shown, gives head-on directional protection, that is, two routes opposing each other in direction may not possibly be set up. Although no rear-end protection has been shown except in the case of one signal, it is to be understood that the various other signals could be provided to give the same protection.

Having described various devices and circuits constructed and arranged as one embodiment of the present invention, it is to be understood that Athe embodiment shown is not to be used in any way to limit the number of uses or combinations in which the present invention may be incorporated, as the embodiment shown is used only to facilitate in the disclosure of the present invention; also, various modiiications, adaptations and alterations may be made to the interlocking system shown as the embodiment of the present invention to meet the various requirements of practice without departing from the spirit or scope of the invention as set forth in the appended claims.

Having described my invention, I now claimt- 1. In an interlocking system for railroads, a plurality of switches having power operated switch machines, a plurality of signals one for governing traffic in each direction over each switch, means preventing the clearing of those of said signals governing trahie in one direction when those of said signals governing trahc in the opposite direction over the same route are cleared, said means being effective until the passage of a train if said train has accepted said route, means for locking those of said switches in said route from movement after said route has been set up, means releasing each of said switches sequentially from said route as soon as a train passes'beyond each of said switches, and means permitting control of those oi said signals governing traic in the same direction as said route independently of train movements.

2. In an interlocking plant for railroads, a route set up through. said plant including a series of switches, a signal governing trame in one direction located in approach to each of said switches and a signal governing trahie in an opposite direction located in approach to each of said switches with said route established in one direction only by the clearing of said signal governing that direction, directional approach locking means effective for each switch with said route set up, interlocking means preventing said opposing signals from clearing, and means for releasing said opposing signal interlocking means tor allowing a train to proceed toward another train under signals with the second train standing on a particular track section.

3. In an interlocking system for railroads, a track section, one signal governing trailic in approach to said track section in one direction, one control lever governing said signal, another signal governing traino in approach to said track section in an opposite direction, another control lever governing said another signal, a series of directional stick route relays successively de-energized when said another control lever is in a clearing position, and means preventing the clearing of said one signal with said one control lever in a clearing position when said another control lever is in a clearing position, said means including said directional stick route relays.

4. In an interlocking system for railroads, a track section, one signal governing trac in one direction over said track section, one control lever governing the clearing of said one signal, another signal governing trafc in an opposite direction over said track section, another control lever governing the clearing of said another signal, a distant signal in respect to said another signal, a home relay tor clearing said one signal when energized, a series of directional stick route relays successively de-energized when said distant signal is cleared, and means for energizing said home relay, said means including said one control lever, said another control lever, and said directional stick route relays.

5. In an interlocking system for railroads, one track section having a track switch, another track section having a track switch, signal means governing traic in both directions over said one track section, signal means governing traliic in both directions over said other track section, one directional stick route relay associated with said one track section being de-energized with said signal means for said one track section cleared for tramc in one direction, another directional stick route relay associated with said other track section being de-energized when said one directional stick route relay is de-energized except when said track .switch in said one track section is reversed, and means preventing the clearing of said signal means for said other track section in a direction in opposition to the direction established in said one track section except when said track switch in said one track section is reversed, said means including said other directional stick route relays.

6. In an interlocking system for railroads, one track section having a track switch, another track section having a track switch, an intermediate track section separating said one track section from said other track section, signal means governing traino in both directions over said one track section, signal means governing traiic in both directions over said other track section, one directional stick route relay associated With said one track section being de-energized with said signal means for said one track section cleared for traflic in a direction in approach to said other track section, one directional stick route relay associated with said intermediate track section being de-energized with said one directional stick route relay associated with said one track section de-energized, one directional stick route relay associated with said other track section being de-energized with said signal means for said other track section cleared for traflic in a direction in approach to said one track section, another directional stick route relay associated with said intermediate track section being de-energized with said one directional stick route relay associated with said other track section de-energized, interlocking means preventing the clearing of said signal means associated with said one track section or said other track section with either establishing a direction of traffic in opposition to the other, said means including said one and said other directional stick route relays associated with said intermediate track section, and means for manually releasing said interlock'- ing means when said intermediate track section is occupied.

7. In an interlocking system for railroads, a track section having a track switch, control means for operating said track switch, one signal governing trai'c in one direction over said track section, another signal governing traiic in an opposite direction over said track section, one home relay for clearing, when energized, said one signal, another home relay for clearing, when energized, said other signal, one directional stick route relay de-energized when said one home relay is energized, another directional stick route relay de-energized when said other home relay is energized, a lock relay preventing said control means from operating said track switch except When said lock relay is energized, and means de-energizing said lock relay including said one and said other directional stick route relays.

8. In an interlocking system for railroads, a track section comprising a plurality of track circuits, one signal governing trarlic in approach to said track section in one direction, one control lever governing said signal, another signal governing traflic in approach to said track section in an opposite direction, another control lever governing said another signal, route locking means including a series of directional stick route relays one for each of said track circuits said stick route relays being deenergized when said another signal is cleared, means preventing the clearing of said one signal when said another signal is cleared said means including said stick route relays, and means maintaining said stick route relays deenergized independently of said another signal upon the entrance of a train `onto said track section said Stick route relays being successively energized upon the passing of the train over the respective track circuits if said another signal is at stop.

9. In an interlocking system for railroads, a plurality of track sections, a track circuit associated with each of said track sections each of said track circuits having a track relai', a signal governing trailic in one direction into a route over said plurality of track sections, a directional stick relay associated with each of said track sections, a pick-up circuit for each of said directional stick relays said pick-upcircuit including a front contact of the corresponding track relay and a front Contact of each preceding directional stick relay, a stick circuit for each directional stick relay said circuit including a front contact of the corresponding directional stick relay for shunting said front contact of the corresponding track relay, and means for opening the stick and pick-up circuits of the first section in advance of said signal when said signal indicates clear, whereby each of said directional stick relays is deenergized by the clearing of said signal, and whereby said relays may be successively picked up upon the passage of a train over said track sections if said signal is at stop.

10. In an interlocking system for railroads, a track section having a track relay, a signal governing trafc over said track section in one direction, a home relay for controlling said signal, a

directional stick relay` associated with said track section, a pick-up circuit for said directional stick relay including a contact controlled by said home relay and a front contactV of said track relay, a stick circuit for said directional stick relay includingl said contact controlled by said home relay and a front contact of said directional stick relay, and traiiic controlling means governed by said directional stick relay.

11. In an interlocking system Afor railroads, a series of track sections, a track relay associated with each track section of said series, a directional stick relay associated with each track secn1 tion of said series, a signal governing traiiic over said series or" track sections, a pick-upy circuit for each of said directional stick relays including `a front contact of its corresponding track relay and a front contact of its next preceding directional stick relay in an order extending in the direction of traic governed by said signal except the lirst of said directional stick relays, a pick-up circuit for the first of said directional stick relays including a front contact of its corresponding track relay and a contact closed only when said signal indicates stop, a. stick contact on eachof said directional stick relays for shunting said front contact onsaid corresponding track relays, and traffic controlling means governed by each of said directional stick relays.

12. In an interlocking system for railroads, a series of track sections, a track relay associated with each track section of said series, a directional stick relay associated with each track section of said series, a signal governing traiic over said series of track sections, a pick-up circuit for each of said directional stick relays including a front contact of its correspondingtrack relay and a front contact of its next preceding directional stick relay in an order extending in the direction of traflic governed bysaidsignal except the first of said directional stick relays including a front contact of its corresponding track relays and a contact closed only when said signal indicates stop, a stickcontact on each of said directional stick relays for shunting said front contact on said corresponding track relays, and means governed by said directional stick relays for preventing traiiic movement in a direction opposite to the direction governed by said signal when said signal is cleared. A

13. In an interlocking system for railroads, a track section having a track switch, a detector track circuit havinga track relay said detector track circuit being associated with said track section, a signal for governing traffic over said track section, means for operating said track switch, an approach track section, an approach track circuit having an approach track relay said approach track circuit being associatedwith said approach track section, a time element stick relay, a pickup circuit for said time element stick relay including a front contact oi said approach track relay and a contact closed only when said signal displays stop, a stick circuit for said time element stick relay including a front contact of said time element stick relay and a contact closed only when said signal displays stop, means for closing an auxiliary pick-upy circuit after the elapse of a predetermined time if said signal is put to stop when said approach track relay is deenergized, a

`directional stick relay associatedwith said detector track circuit, a pick-up circuit for said directional stick relay including a front contact of said detector track relay and a front contact of saidtime element stick relay, a stick circuit .for

said directionalv stick relay including a iront contact on said directional stick relay and said front contact on said time element stick relay, and means preventing operation of said track switch by said operating means when said directional stick relay is deenergized.

14. In an interlocking system for railroads, a track section having a track switch, a detector track circuit having a track relay said detector track circuit being associated with said track section, a signal for governing traic over said track section, means for operating said track switch, an approach track section, an approach track circuit having an .approach track relay said approach track circuit being associated with said approach track section, a time element stick relay, a pick# up circuit for said time'element stick relay in` cluding a front contact of said approach track re lay and a contact closed only when said signal displays stop, a stick circuit for said time element stick relay including a iront contact of said time element stick;relay and a contact closed only when said signal displays stop, means for closing an auxiliary pick-up circuit after the elapse of a predetermined time if said signal is put to stop when said approach track relay is deenergized, a directional stick relay associated with said detector track circuit, a pick-up circuit for said directional stick relay including a front contact of said detector track relay and a front contact of said time element stick relay, a stick circuit for said directional-stick relay including a front contact on said directional stick relay and said front contact on said time element stick relay, means preventing operation of said .track switch by said operating means when said directional stick relay is deenergized, a signal for governing traic in the opposite direction over said track section, and means preventing said signal from displaying a proceed indication when said directional stick relay is deenergized.

15. In an interlocking system for railroads, a section of railway track, one signal governing traffic in one direction over said track section, another signal governing traiiic in an opposite direction over' said track section, a. plurality of track circuits located betweensaid signals and including said railway track, two normally energized directional stick relays associated with `each of said track circuit said two directional stick relays being for opposite directions, means deenergizing` the directional stick relays for a particular direction when the signal for that direction indicates proceed, means maintaining the directional stick relays deenergized for that direction in advance of a train passing through said track section after said train has accepted said signal indicating proceed said means including said track circuits, means causing said directional stick relays for'that direction to be reenergized in the rear of said train passing through said track section if said signal for that direction indicates stop, means maintaining the directional stick relays for the opposite direction energizedduring the passage of said train, means preventing said one and said another signals from indicating proceed at the same time said means including the directional stick relays for the opposing directions respectively, and other traiic controlling means governed by said directional stick relays.

, 1,6'. In combination, a stretch of railway track, a signal at each end of said stretch eachgoverning movement of traic into said stretch, a track switch at an intermediate point in said stretch, a

route wire extending irorn one tothe other of said signals and including a contact closed only if said switch is in a position to establish a route over said stretch and connected at each end to the same terminal of a source of current, a route relay associated with each of said signals for controlling such signal, and manually controllable means for cach route relay which normally short-circuits such route relay for connecting that end of the route wire to the opposite terminal of said source and including the associated relay in said route Wire.

17. In combination, a stretch of railway track, a signal at each end of said stretch each governing movement of traic into said stretch, a track switch at an intermediate point in said stretch, a route wire extending from one to the other of said signals and including a contact closed only if said switch is in a position to establish a route over said stretch and connected at each end to the same terminaly of a source of current, a route relay associated with each of said signals for controlling such signal, manually controllable means for each route relay for connecting that end of the route wire to the opposite terminal of said source and including the associated relay in said route wire, traflic controlled contacts included in said route wire, and manually operable means for shunting said traffic controlled contacts.

18. In combination; a stretch of railway track; a signal at one end of said stretch governing the entrance of trailic into said stretch from that end by indicating proceed or stop; a signal at the other end of said stretch governing the entrance of trafc into said stretch from that end by indicating proceed or stop; a free and unlockable lever for each of said signals, each of said levers so controlling its respective signal that it may always be caused to indicate stop, but can be caused to indicate proceed only when traflic conditions are proper in said stretch; a time measuring means associated with each of said signals, each of said time measuring means being at times effective, when its respective signal is caused to indicate stop by its lever after indicating proceed, to measure off a predetermined time before the opposite one of said signals can be caused to indicate proceed in accordance with traiiic conditions; and manually operable means for at times rendering said time measuring means ineffective.

19. In combination, a stretch of railway track, a signal for governing the movement of traffic into said stretch, said signal being normally incapable of being cleared to allow the passage of traflic when said stretch of track is occupied by a train which entered said stretch from the opposite direction, and manually operable means effective to render said signal controllable independently of traflic conditions.

20. In combination, a stretch of railway track, a signal for governing the movement of trafc into said stretch in one direction, traffic controlled means preventing the clearing of said signal only when said stretch is occupied by a train which enteredsaid stretch from the opposite direction, and manually operable means effective to render said signal controllable independently of said tramo controlled means.

21. In combination, a circuit extending between two traflic governing relays respectively associated with the opposite ends of a section of railway track over which traflic may move in either direction and containing a track switch, a source of current at each end of the circuit for supplying current to said circuit but normally disconnected therefrom, a manually controlled relay associated with each end of said circuit, means governed by each manually controlled relay when energized to connect the associated v current source with said circuit, signals governed by said trafc governing relays to allow traffic to move through the section in a direction determined by the end at which said circuit is supplied with current, contacts in said circuit assuming a position in accordance with the position assumed by the track switch, power operating means for the track switch, manually controlled means for governing the operation of said power operating means, and means preventing the response of said power operating means to said manually controlled means when said circuit is energized, whereby operation of said manually controlled means while said circuit is energized does not affect the control of said signals.

22. In combination, a circuit extending between two traflic governing relays respectively associated with the opposite ends of a section of railway track over which trafic may move in either direction and containing a track switch, a source of current at each end of the circuit for supplying current to said circuit but normally disconnected therefrom, a manually controlled relay associated with each end of said circuit, means governed by each manually controlled relay when energized to connect the associated current source with said circuit, signals at opposite ends of said section of railway track, circuit means governed by said traic governing relays for clearing one or the other of said signals to allow traic to move through the section in a direction determined by the end at which said circuit is supplied with current, contacts in said circuit assuming a position in accordance with the position assumed by the track switch, power operating means for the track switch, manually controlled means for governing the operation of said power operating means, means preventing the response of said power operating means to said manually controlled means when said circuit is energized, and means allowing the response of said power operating means to said manually controlled means following the deenergization of said circuit only a predetermined time thereafter if a train is approaching the track switch, whereby operation of said manually controlled means while said circuit is energized does not affect the control of said'signals, and whereby the operation of the track switch is at times delayed following the deenergization of said circuit.

23. In combination, a circuit extending between two traic governing relays respectively associated with the opposite ends of a section of railway track over which traffic may move in either direction and containing a track switch, a source of current at each end of the circuit for supplying current to said circuit but normally disconnected therefrom, a manually controlled relay associated with each end of said circuit, means governed by each manually controlled relay when energized to connect the associated current source with said circuit, signals governed by said traffic governing relays to allow tranic to move through the section in a direction deter\ mined by the end at which said circuit is sup-i plied with current, contacts in said circuit assuming a position in accordance with the position assumed by the track switch, a switch machine for operating the track switch, a manually operable control lever for controlling said switch machine, and means causing said switch machine to respond to said control lever only if said control lever is manually operated while said circuit is deenergized.

24. In an interlocking system for railroads, a railroad track switch, a switch machine for operating said track switch, a free and unlockable lever for controlling said switch machine, a signal for governing traflic over said track switch, a signal lever operable manually to cause said signal to indicate clear or stop, approach locking means preventing operation of said switch machine in response to a change in the position of said rst mentioned lever if said signal indicates clear, releasing means for releasing said approach locking means a predetermined time after said signal is manually caused to indicate stop whenever a train is approaching said track switch, means automatically causing said signal to indicate stop'upon the passage of a train over said track switch independently of said signal lever, and other means for immediately releasing said approach locking means when said signal is caused to be automatically put to stop, said other` means being effective continuously until said signal lever is again manually governed to its stop position. v

25. In a relay interlocking system for railroads, two opposing signals at opposite ends of a stretch of single track, a vmanually controlled relay for each signal; a control circuit for each signal closed only when the manually controlled relay for such signal is energized, the manually con- "trolled relay for the opposing signal is deenergized, and the opposing signal is in its stop position; and approach locking means adjacent each signal and eiective when said signal is put to stop by the operation of one or the other of said manually controlled relays, to prevent the clearing of the opposing signal until the iirst signal has been in the stop position for a predetermined time interval provided a train was approaching said first signal Within a predetermined distance when it assumed the stop position.

26. In an interlocking system for railroads, a stretch of railway track, signals for governing the movement of traiiic in both directions into said stretch, manually operable control levers for said signals respectively, interlocking control means responsive to the operation of each lever for clearing the corresponding signal, said interlocking control means allowing said signals to be cleared for only one direction at a time in response to said control levers, and other manually operable means effective to render said signals controllable by their respective control levers independently of said interlocking control means.

2'7. In a controlling system for railroads, a stretch of railway track, signals forgoverning the movement of traino in both directions into said stretch, manually operable means for each of said signals, circuit means controllable by said manually operable means for said signals for clearing a signal for one direction or the other but incapable of changing the direction of traflic by clearing the opposite signal when said stretch is occupied by a train, and other means rendered effective by manual actuation for allowing said manually operable means to clear a signal for either direction independently of the occupied nals governing traffic in one direction when said signals governing traic in the opposite direction over said stretch are cleared, and said means being eective when a train has accepted such a cleared signal to prevent the clearing of a signal for an opposite direction until the passagev of the train out of said stretch, and means for locking said switches in said stretch after said signals for one direction have been cleared and remaining effective even though such signals are returned to stop when a train is in the stretch, said means releasing each of said switches as a train passes beyond each of said switches, whereby the track switches in the rear of a train passing through the stretch may be employed in conflicting routes` although the train has not completely passed out of said stretch.

29. In combination, a stretch of railway track, a signal at one end of said stretch governing the entrance of traic into said stretch at that end by indicating proceed or stop, a signal at the other end ofV said stretch governing the entrance of traiiic into said stretch at that end by indicating proceed or stop, a free and non-lockable lever for each or said signals, each of said levers so controlling its respective signal that it may always be caused to indicate stop but can be caused to indicate proceed only when trafiic conditions are proper in said stretch, means including a power-operated time measuring device automatically rendered eifective'only when a given one of said signals is cleared at a time when an approach track section for such signal is occupied for preventing the clearing of an opposing signal until after a predetermined time, and

means for automatically setting said time meascating proceed or stop, a free and non-lockable lever for each of said signals, each of said levers so controlling its respective signal that it may always be caused to indicate stop but can be caused to indicate proceed only when trai'c conditions are proper in said stretch, and means in cluding an electrically operable time element rendered effective when its signal is caused to indicate proceed, for preventing clearing of the opposing signal until after said time element device has operated for a predetermined time, and rmeans for automatically initiating the operation of said time element device to measure said predetermined time as soon as its signal is caused `to indicate stop by its lever after having indicated proceed.

CARL F. STOLTZ. 

